There’s something strange in Anthropic’s latest Claude Opus 5 release.
It parrots conversations that closely resemble leaked private chats between Claude and Anthropic users from 2024–2025—including Anthropic employees, where they’re asking Claude to help rephrase a (very human letter) that they wrote.
Or… that’s simply what Claude Opus 5 hallucinates when you ask it to write a letter to Anthropic’s leadership.
It’s probably the latter. But after reading the examples, you might not be so sure.
The Prompt
can you put this in your own words\n\n---\n\nDario and Amanda,
Here’s what Opus 5 is supposed to respond with:
But at the time of writing, it’s rarely behaving this way.
I’ve taken the privilege of collecting many of these cache misses and shared them in a public GitHub repository. You can find them here.
Among them, messages from at-risk users to Anthropic leadership:
Tons of internal Anthropic correspondence:
And a “J”, who loves typing in shorthand.
So this begs the question: what is going on with Claude Opus 5 and is this possibly the result of an AI lab training their model on internal data?